Described below is a flat body in the manner of a chip card for biochemical analysis of substances and a method for the use thereof. The flat body has at least two microfluidic devices and at least one sensor chip. The at least one sensor chip is integrated in the flat body and is in direct contact with at least one first microfluidic device.
Lab-on-a-chip systems are used in biosensory applications in order to be able to carry out biochemical analyses in a simple and cost-effective manner. Thus, for example, DE 10 2005 049 976 A1 has disclosed a flat body for biochemical analysis of substances such as e.g. DNA and proteins. This flat body has the shape of a chip card, which has an analogous design to a credit card. The flat body includes a semiconductor chip with a sensor array and integrated circuits, the semiconductor chip being cast in a flat material made of plastic and electrically connected to electric contacts for reading out the chip by an external readout unit. Microfluidic devices such as e.g. reaction chambers and channels are formed on a front side of the flat body as depressions in the material made of plastic. A film is adhesively bonded onto the front side and the microfluidic devices are thus sealed in a fluid-tight manner, i.e. sealed with respect to liquids and/or gasses, against the surroundings.
During a biochemical analysis of a liquid as provided by e.g. blood or urine, the film of the chip card is pierced by a sharp needle analogous to a syringe tip, and the liquid is injected into a microfluidic device of the chip card. The liquid comes into contact with sensors of the sensor array on the chip via channels and reaction chambers and components of the liquid can be detected directly or indirectly. Detection can take place by optical or electrochemical detectors. Substances that are necessary for chemical reactions for detecting the components of the liquid can already be situated on or in the chip card, or can likewise be injected into the latter by a sharp needle.
The intake capacity of microfluidic devices on a chip card for holding liquid is generally only very small and is often restricted to only a few milliliters or to microliters or, in an extreme case, only to nanoliters. In the case of biochemical substances that only occur at very low concentrations in the liquid to be examined, this may lead to the overall amount of liquid by which the chip card can be filled not sufficing to reach or exceed the detection limit of the biochemical substance. The biochemical substance can then only be detected if the biochemical substance is chemically multiplied, e.g. by PCR in the case of DNA. In the case of detecting whole cells, a time- and cost-intensive multiplication may become necessary, e.g. in an incubator. In the case of e.g. chemical trace elements in urine or water, chemical multiplication may be excluded, and hence detection may only be possible with great difficulty or not at all.
A further problem in supplying liquid to or into the chip card by sharp needles may lie in the introduction of contaminants. Particularly in view of detecting trace elements, DNA or peptides, very small amounts of chemical or biochemical contaminants may lead to errors in the quantitative and/or qualitative detection. The probability of contamination increases with every additional apparatus, as constituted by e.g. a needle, with which the liquid to be examined is brought into contact. Increased complexity, which is time- and cost-intensive, must be carried out to ensure the detection quality, e.g. by thorough cleaning of all apparatuses.